1. Field of the Invention
The present invention relates generally to broadband wireless access communication systems, and more particularly to methodologies in requesting and allocating uplink bandwidth according to qualities of service (QoS) in a broadband wireless access communication system.
2. Description of the Related Art
A fourth generation (4G) wireless communication system, which is a next generation communication system, is actively being designed and studied in order to provide users with multiple services having various QoS at a high transmission rate. Current third generation (3G) wireless communication systems support a transmission speed of about 384 kbps in an outdoor channel environment having a relatively unfavorable channel environment and support a maximum transmission speed of 2 Mbps in an indoor channel environment having a relatively favorable channel environment. Further, wireless local area networks (LAN) systems and wireless metropolitan area networks (MAN) systems generally support transmission speeds of 11 to 50 Mbps. Accordingly, in current 4G communication systems, research is actively being conducted to develop a new type of communication system for ensuring mobility and QoS in wireless LAN system and wireless MAN system, which support the relatively high transmission speeds and high speed services that are to be provided by the 4G communication system.
For the end user, the most important thing in broadband wireless access communication networks is satisfaction with the end-to-end services regarding the QoS. The QoS requirements are mapped to the protocol hierarchy levels. For enabling a mapping between different hierarchy levels, the QoS requirements are usually classified. The QoS requirements also have to be fulfilled connection-specific. Additionally, it should be noted that in many cases, one subscriber station may have several connections simultaneously. These connections, each identified by a unique connection identifier (CID), may originate from more than one user equipment, and they have a defined QoS, which may be different for each connection. Thus, there is a problem as to how the QoS requirements can be fulfilled for each connection.
Some 4G broadband wireless access communication systems utilize four levels of QoS: (1) Unsolicited Guaranteed Service (UGS): UGS Service needs the same bandwidth to be continuously allocated while maintaining a connection such as VoIP (Voice over Internet Protocol); (2) Real-time Packet Service (rtPS): a real-time voice transmission service has the characteristics of a real-time service like an UGS, but causes variable bandwidth allocation because the amount of generated data is different depending on the frames and conforms to video transmission; (3) Non-real-time Packet Service (nrtPS): service having no real-time service characteristics, does not have a burst characteristic as opposed to the best effort service, and conforms to an FTP (File Transfer Protocol); and (4) Best Effort (BE) having a burst characteristic, conforms to best effort services and the like, service of the lowest class, has an allocation of bandwidth in a non-assured form, allocates bandwidth only for each request (i.e., TCP/IP).
In centrally controlled access systems, capacity is typically granted subscriber station-specific. Problems may arise when the subscriber station receives an insufficient data grant among multiple connections. FIG. 1 shows a prior art example of GPSS (Grant Per Subscriber Station) operation and the problems arising from insufficient data grants in prior art broadband wireless access communication systems. The system includes a subscriber station (SS) and a base station (BS). The subscriber station has three resource requests for three separate connections 102, 104 and 106. These connections may represent connections of three single user terminals, or three connections of a single user terminal with different QoS requirements. Each connection is identified in row 108 as “CID1,” CID2,” and “CID3,” and further indicates the type of service for each CID as UGS rtPS, nrtPS, respectively. The connections 102, 104, 106 have separate resource requests of 600, 500 and 300 bytes, respectively, as shown in row 110.
The subscriber station sends a capacity request 112 to the base station of 500 bytes for CID2 and 300 bytes for CID3, for an aggregate request of 800 bytes. A capacity request is not required for CID1 because it is under the UGS QoS, and is being provided a periodic capacity grant by the base station without the need for continuing requests. The base station decides to allocate only 600 bytes of the aggregate request of 800 bytes, and sends a resource grant message 114 granting the 600 bytes.
Upon receipt of resource grant message 114, the subscriber station allocates the 600 byte grant equally among the different connections. The subscriber station transmits a response message 116 providing updated data to the base station according to the capacity allocation decisions made by the subscriber station. Message 116 indicates that each connection was allocated 200 bytes, resulting in three separate allocation fragments. As a result, the first connection updated resource need is 400 bytes more, the second connections need is 300 bytes more, and the third connection's need is 100 bytes, as seen at row 118. This results in the subscriber station transmitting an additional resource request 120 for 300 bytes for CID2 and 100 bytes for CID3
The base station then responds by granting 1,000 bytes in message 122, which includes its periodic grant of 600 bytes to CID1 under its UGS QoS, as well as granting in-full the additionally 400 bytes requested in message 120. As seen at row 124, each of the three connections 102-106 have fully satisfied their current resource needs from the 1,000 bytes granted by the base station. However, this process has resulted in the base station granting the subscriber station 200 bytes more than is needed for the subscriber station to fulfill its uplink capacity requirements. The subscriber station responds with an update message 126 reporting that each of the connections CID1, 2 and 3 have uplinked an additional 800 bytes to the base station.
As will be appreciated, this example shows that a UGS connection can steal bandwidth from non-UGS connections based on outstanding resource requests within the subscriber station. Moreover, since the UGS type of service has guaranteed, unsolicited bandwidth allocated at periodic intervals, the UGS connection should not be allowed to steal from a solicited data grant to the non-UGS connections. Moreover, it can be seen that the re-allocation of the data grant among the various connections results in multiple fragmentations on all connections, which can be time consuming in allocating and subsequently fulfilling the resource request. Last, as was seen in the example above, such fragmentation will often result in more bandwidth being requested than is needed to fulfill the resource needs.
What is needed is a mechanism for implementing a proper schedule of all connection uplink data requests that satisfies the required QoS parameters for each connection without suffering from the aforementioned problems. The subscriber station needs to intelligently share an insufficient data grant among uplink data demands of connections, and must guarantee the high data rates needed for high QoS connections. Moreover, the subscriber station needs to institute a methodology of allocating insufficient data grants that prevents a high QoS service from stealing bandwidth granted to lower levels of QoS connections. Still further, such a methodology should minimize fragmentation to increase uplink throughput.
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced.